Novel one-component molecular glass photoresist based on cyclotriphosphazene containing t-butyloxy carbonyl group for i-line lithography

Abstract

Hexakis(4-formylphenoxy) cyclotriphosphazene (HAPCP), substitution reaction product of hexachlorotriphosphazene (HCTP) with p-hydroxybenzaldehyde, was reduced by sodium borohydride to afford hexakis[4-(hydroxymethyl) phenoxyl] cyclotriphosphazene (HHPCP). The hydroxyl group of this compound was then protected by the reaction with di-tert-butyl dicarbonate ester (DBDC) in the presence of 4-dimethylaminopyridine (DMAP) as catalyst to give t-butyloxy carbonyl (tBOC) protected HHPCP. Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (¹H NMR) were employed to characterize the chemical structure, indicating that the synthesis was successful. Thermal behavior was characterized by thermogravimetric analysis (TGA), the results showed that the initial thermal decomposition temperature occurred at approximately 170 °C, X-ray diffraction analysis (XRD) results showed that the tBOC protected HHPCP derivatives had amorphous form, and performed excellent film-forming property. Upon irradiation to 365 nm exposure, the photoacid generated proton H⁺, which can catalyze the deprotection of acid labile tBOC group. This type of novel molecular glass photoresist based on hexachlorotriphosphazene showed high sensitivity, making it possible to fabricate 1 μm line and space pattern under i-line exposure.

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